After 13 years of war, Bashar al-Assad’s regime in Syria has been defeated. What comes next?

The early days of the uprising against Bashar al-Assad’s Syrian regime — which came to a stunning end this weekend after 13 long years of civil war as rebel forces entered the capital of Damascus and Assad fled into exile — were defined by two famous pieces of graffiti.

The first was written by a group of teenage boys on a school wall in early 2011 in the city of Daraa. Inspired by the Arab Spring protests then seemingly sweeping away the old order in longtime dictatorships like Tunisia, Egypt, and Libya, they wrote, “You are next, doctor,” referring to Assad, who had trained and worked as an ophthalmologist in London in his early years before returning to take over the family business of ruling Syria with an iron fist. The boys were then arrested and tortured by the regime’s security forces, an event credited by many with sparking the mass protest movement against Assad.

The message proved to be overly optimistic: Assad didn’t flee and he didn’t compromise, instead opting to crush the uprising by force, leading to a civil war that would kill as many as half a million people and displace millions more.

The second graffiti message was a slogan scrawled by pro-regime militias throughout the country in the early days of the uprising: “Assad or we burn the country.” The phrase signaled the regime’s complete unwillingness to compromise with its enemies and the lengths it would go to stay in power.

Over the past week, even as the rebels took the ancient city of Aleppo on November 30 and began streaming down the highway south toward Damascus, it still seemed far-fetched that the Syrian regime would fall — that a family that had been in power since Bashar’s father Hafez al-Assad carried out a coup 54 years ago and was willing to go so far as to use chemical weapons on its own people and reduce its own cities to rubble to preserve that power would simply crumble in a matter of days.

But that’s exactly what happened: As the rebels advanced, there were numerous reports of government forces simply abandoning their positions and discarding their uniforms. The Russian government says it has offered Assad and his family asylum. US officials say they have not confirmed that Assad is in Russia, but have no reason to doubt it.

Today, footage from Damascus is showing the kind of celebrations not seen since the heady early days of the Arab Spring. Videos on social media show people who were imprisoned, including small children and people who’ve been incarcerated for decades, being released from the regime’s notorious prisons. The events of the past week have raised hopes among at least some of the more than 6 million Syrians who’ve fled the country — forming the world’s largest refugee population — that they may be able to return home.

The White House initially distanced itself from the events in Syria, after the fall of Aleppo. But on Sunday, President Joe Biden spoke from the White House calling Assad’s fall a “fundamental act of justice” and a “moment of historic opportunity.” His statement also linked the event to the US support for Ukraine and Israel in their fight against Russia, Hezbollah, and Iran, all key backers of the Assad regime.

The initial caution to embrace the offensive wholeheartedly was due in no small part to the fact that the main group leading the opposition, Hay’at Tahrir al-Sham (HTS), is a former affiliate of al-Qaeda that is still designated as a terrorist organization by the US. On a background call on Sunday, a senior US administration official said that the US “intends to engage with [HTS] appropriately and with US interests in mind,” but would not comment on whether it would reconsider the group’s terrorist designation.

There are looming questions over issues including the fate of Assad’s chemical weapons and the fate of Syria’s religious minorities, including the Kurdish forces that have allied with the American military to fight ISIS. Seemingly driving this point home, the US conducted dozens of airstrikes targeting ISIS in Syria on Sunday as part of what US Central Command called an effort to “ensure that ISIS does not seek to take advantage of the current situation to reconstitute in central Syria.” For American policymakers, the scenes in Damascus could reawaken memories of Iraq and Libya — countries where longtime dictators were toppled, only to see their countries consumed by sectarian violence and terrorism.

One key difference this time around is that Assad was toppled by a mostly homegrown uprising, rather than a US-led military intervention. Not that the US has been totally absent from the scene. American military forces carried out a strike on Iranian militia targets in Syria on December 3, though the Pentagon was quick to stress that this was in response to a threat to American forces, not in support of the rebels.

The rebel forces also include the controversial Turkish proxy group known as the Syrian National Army (SNA) , and it appears likely Ukraine’s intelligence services may have played some role in assisting the offensive by fellow opponents of the Russian military. It’s worth noting that the fighters entering Damascus also included a new rebel group from southern Syria dominated by veterans of the Free Syrian Army, which for years was backed by the US and other western powers.

But as of now, as Biden suggested, it looks as if the biggest role international actors played in assisting the rebels was indirect and took place outside of Syria itself: After 14 months of war with Israel, Assad’s ally Hezbollah was not in a position to intervene on Assad’s behalf, as it has in the past; with its main military assets tied up in Ukraine, neither was Russia.

Attention will now turn to Syria’s new rulers and how they will govern. Abu Mohammed al-Jolani, the HTS leader, has said all the right things, calling on its supporters to avoid vengeance against regime supporters. For now, he is leaving Assad-appointed Prime Minister Mohammed Ghazi al-Jalali in place until a transitional government is formed.

On Saturday, a few hours before Assad’s overthrow, Vox asked Mouaz Moustafa, executive director of the US-based Syrian Emergency Task Force, what a transitional government could look like. He suggested that UN Resolution 2254, adopted back in 2015 but never implemented, could provide a road map: It calls for a Syrian-led political process facilitated by the United Nations leading to new elections within 18 months.

In the coming months, we’ll see whether Jolani, the former al-Qaeda fighter with a $10 million price on his head from the US government, is really the pragmatic pluralist he now says he is, and assuming he is, whether he’s capable of keeping together an ethnically and religiously diverse country, one awash with weapons, various armed groups, and traumatized by decades of dictatorship and war.

A big question mark is how Damascus’s new rulers will contend with the Kurdish-ruled northeast corner of the country, particularly if the incoming Trump administration follows through on plans from his last term to remove US troops from the region. There have already been concerning reports in recent days of clashes between Kurdish forces and the Turkish-backed SNA. On Saturday, Trump posted on Truth Social that the offensive in Syria was “NOT OUR FIGHT” and that America “SHOULD HAVE NOTHING TO DO WITH IT.”

Beyond these questions, Assad’s fall should be a reminder of some important facts. One, governments and analysts continue to be extremely bad at assessing the strength of non-state militant groups like HTS, their ability to launch major offensives, and the ability of governments to resist them.

Two, authoritarian regimes are often much weaker than they appear. As the just-freed Russian dissident Vladimir Kara-Murza recently told Vox, referring to his own country, “In these repressive, tyrannical regimes, you don’t know what’s happening beneath the surface … there may be problems developing for the regime, but nobody’s aware of them until they come out of the open and suddenly everything collapses.”

Over the past few years, the world had all but decided that Assad had won the civil war. Regional governments that had spent years trying to topple him were welcoming him back into the fold, while the US was moving on to other priorities. If the last few days teach us anything, it’s that governments like Assad’s can often be more brittle than they appear from the outside, and it just takes a strong push to knock them over.

For all the very justified concern and caution about what lies ahead for Syria, that should be some cause for optimism.